Inlet filter

ABSTRACT

An inlet filter for use with stormwater drains and roof drains. The filter is formed of a mat of natural or synthetic fiber material with netting bonded on one side. A convenient method for attaching the filter to a drain using cable ties or adhesive is provided.

FIELD OF THE INVENTION

The present invention relates generally to inlet filters, and in particular, inlet filters for use on stormwater drains and roof drains, and a method for installing an inlet filter on a drain.

BACKGROUND OF THE INVENTION

Stormwater drains are provided in streets, roads, parking lots and the like to permit water runoff to be directed into underground catch basins and drainage pipes. The drains are provided with a grate to screen out larger debris and to prevent persons and vehicles from falling into the drains. The grates may be of various configurations, such as flat, roll curb, vertical or beehive.

It is desirable to keep silt and sediment from entering a drain to avoid clogging of catch basins and drainage pipes. This is especially true on a construction site, where large quantities of silt, sediment and other debris may be present. In the construction of streets, highways, residential housing developments and shopping centers and other commercial developments, it is typical to first lay out the streets. Then, the stormwater drainage system is installed. This system includes underground drainage pipes, culverts, catch basins and drop inlets that connect the underground parts of the system to a finished street-level drain inlet, such as a roll curb inlet with grate. As construction continues, considerable sediment and debris may be generated, which will be pushed by rain, wind and gravity towards the drains. Building codes, municipal regulations and environmental rules often require that such debris be prevented from entering the storm drain system. Simultaneously, the drains must be kept open and functional to permit rain water to drain.

Roof drains are provided in flat roofs, such as those on large commercial buildings, to drain rainwater. These drains are typically fitted with flat or beehive grates. Like stormwater drains in streets, roof drains need to be kept clear of sediment and debris so that water drains freely and does not accumulate on the roof where it can cause damage.

Various filters have been used to protect the inlets of the stormwater systems and roof drains, but all suffer from certain disadvantages. One disadvantage with many existing filters is that the grate must be removed from the inlet to install the filter. Other filters are complex and expensive. Those types which fit below the grate inside the drain are difficult to clean or replace.

There is a need for an inlet filter to protect inlets of stormwater and roof drains and prevent sediment from entering the inlet while allowing water to pass through substantially unimpeded. There is also a need for an inlet filter which can be quickly and easily attached to and removed from a drain without removing the drain grate. There is also a need for an inexpensive filter that can be cut to fit in the field and that will fit inlets of various shapes and sizes, such as flat, roll curb, vertical and beehive inlets. There is also a need for an inlet filter that can be readily cleaned without removal from the drain. There is a need for a filter that is resistant to degradation from exposure to ultraviolet (UV) radiation in sunlight. Further, there is a need for a stormwater drain inlet filter that will not be dislodged or damaged by vehicular traffic and will not present a hazard to pedestrians.

SUMMARY OF THE INVENTION

In accordance with the present invention, an inlet filter for a drain inlet having a grate includes a fiber mat and a plurality of flexible locking connectors for insertion through the mat to secure the mat to the grate.

In accordance with a preferred embodiment of the invention, the fiber mat is a natural fiber such as coir fiber, with a thickness and density selected to achieve an acceptable combination of sediment control and water flow, and the flexible connector is a Nylon cable tie.

In another aspect, the invention provides a method for reducing the amount of sediment which enters a drain, comprising placing a filter over the drain inlet and securing the filter to the grate by inserting flexible locking connectors through the mat, passing each connector around a bar of the grate and back through the mat and locking each connector.

In another aspect, the invention provides a method for installing a filter on a drain inlet that includes providing a mat of a size and shape to cover and slightly overlap the inlet, and attaching the mat to the grates by flexible locking connectors passed through the mat and around bars of the grate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an inlet filter in accordance with the invention.

FIG. 2 is an illustration of an inlet filter for installation on a flat street grate.

FIG. 3 is an illustration of an inlet filter for installation on a curb grate.

FIG. 4 is an illustration of an inlet filter for installation on a beehive grate.

FIG. 5 is an illustration of an inlet filter for installation on a beehive grate with an exposed overflow section.

FIG. 6 illustrates a method of installing an inlet filter on a grate.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1, the body of filter 2 is a mat 4 of fiber material with a netting or mesh 6 bonded to the fiber material of mat 4 on one side to provide structural integrity. Preferably, mat 4 is made of a natural fiber such as coir fiber, and mesh 6 is made of fiberglass. However, mat 4 may also be made of a suitable synthetic fiber or a blend of natural and synthetic fibers. The fibers may be bonded together with a binder such as latex. Mesh 6 may be made of another suitable material. The openings in mesh 6 may be generally square and about 3/16 inch on a side, or another suitable shape and size.

In a preferred embodiment, mat 4 is about 1½ inches thick and has a density of about 4.0 OSF (ounces per square foot). This thickness and density of coir fiber have been found to provide a desirable combination of sediment control and water flow. More specifically, a coir fiber mat with these characteristics has been shown to provide a filtering efficiency of 59.1% while maintaining a flow rate of 150 liters/minute when tested with sand sieved through a No. 10 sieve, thus complying with industry standards for silt filtering efficiency and flow rates (e.g., ASTM D 5141). The preferred coir material has also been found to exhibit good UV resistance, tensile properties and smolder resistance.

The inlet filter of the invention may be used on flat street grates as shown in FIG. 2, roll curb inlets as shown in FIG. 3, and beehive-type grates as shown in FIGS. 4 and 5. The filter may be used not only on street drains but also on roof drains of the type typically found on flat roofs of commercial buildings, which may have a flat or beehive grate. Filters may be provided pre-cut to size for standard size grates, e.g., 27×30 inches. Alternately, the filter material may be provided in rolls or sheets and cut to size on site to fit any size or shape drain grate.

Inlet filter 2 is easily attached to the inlet grate with flexible locking connectors 8, i.e., cable ties or “zip” ties. A cable tie consists of a sturdy Nylon tape with an integrated gear rack, and on one end a ratchet within a small open case. Black cable ties are typically used for outdoor applications, as the ultraviolet component of sunlight will degrade clear nylon. Once the pointed tip of the cable tie has been pulled through the case and past the ratchet, it is prevented from being pulled back; the resulting loop may only be pulled tighter.

The method for installing inlet filter 2 will now be described with reference to FIG. 6. First, sediment, debris, ice and snow are removed from the inlet grate surface and the immediate surrounding area, using, e.g., a broom as shown in FIG. 6A. If the filter is not pre-cut, it is now cut to size with a knife or shears. Fit is verified by placing filter 2 over the grate 10 to ensure that filter 2 extends at least one inch beyond all sides of a street grate, or the front and both curb ends of a curb grate. This overlap ensures that the inlet is completely protected, and also slows water flow and starts filtering sediment and debris before water drops into the inlet. Water flow slows as it flows longitudinally through filter 2, allowing sediment to drop, and filtration as water passes through filter 2 transversely further reduces sediment load. Filter is positioned on grate 10 with net 6 side down. In the case of a curb grate, filter 2 is positioned flush to the back edge and extending beyond the grate opening on the front and both sides.

Once positioned, filter 2 is lifted slightly as shown in FIG. 6B so the installer can see the first grate bar 12 from the edge of the grate cover. The installer takes a cable tie 8, pushes its free, pointed end 8 a down through mat 4, and loops tie 8 under grate bar 12 as shown in FIG. 6C. The installer inserts pointed end 8 a of tie 8 about 2 inches away from the first tie penetration and pushes it back up through mat 4. Normally, this may be done by hand without tools; however, the installer may also make a small hole in mat 4 with a screwdriver, awl or pointed stick to facilitate insertion of tie 8. Pointed end 8 a of tie 8 is inserted into the receiving end 8 b just enough to hold the ends loosely. This process is repeated until all of ties 8 are loosely installed as shown in FIG. 6D. Ties 8 are left loose until all of ties 8 are looped through mat 4 around the grate bars. Preferably, eight ties are used for a flat street grate or beehive grate, and seven are used for a curb grate. Of course, the number of ties can be varied depending on the size of the grate. Ties 8 are preferably positioned around the perimeter of the grate as shown in FIGS. 2-4.

After all of ties 8 are attached, filter 2 is repositioned as needed to completely cover and properly overlap grate 10. Free ends 8 a of each of ties 8 are the pulled hand tight to securely anchor filter 2 to grate 10. Excess loose end portions 8 a of ties 8 may be cut off leaving an approximately one inch tail.

Some situations, and some municipal regulations, may require an exposed overflow to accommodate extreme flow conditions. Exposing the emergency overflow section of the drain allows unfiltered water flow when the water depth exceeds the height of the filter. In this case, an opening 14 is cut in filter 2 with a knife or shears to expose the upper portion of the overflow section of the drain as shown in FIG. 5.

Maintenance of the installed filter is simple and convenient. The filter may be cleaned without removing it from the grate, even if ponded water surrounds the inlet. The top and sides of filter 2 are swept with a broom to remove sediment and debris which accumulate after a rain event. In the case of standing water at the inlet, sweeping away built-up debris allows water to drain through the filter.

When construction work is completed or the filter is otherwise no longer needed, or the filter needs to be replaced, it may be easily removed without removing the grate from the inlet, simply by cutting ties 8.

In the case of a roof drain, the filter may be installed using roofing adhesive instead of cable ties. In this case, suitable roofing adhesive is applied to the perimeter of the mesh side of the filter to adhere it to the roof about the perimeter of the drain.

The foregoing is intended to represent one embodiment of the present invention and is not intended to limit in any way the scope of the invention. Additional modifications and enhancements to the invention may be apparent to those of skill in the art. 

1. An inlet filter for a drain inlet having a grate, comprising: a fiber mat; and a plurality of flexible locking connectors for insertion through the mat to secure the mat to the grate.
 2. The filter of claim 1 wherein the fiber is a natural fiber.
 3. The filter of claim 2 wherein the natural fiber is coir.
 4. The filter of claim 1 wherein the fiber is a synthetic fiber.
 5. The filter of claim 1 wherein the fiber mat has a density of about 4.0 OSF.
 6. The filter of claim 1 wherein the fiber mat is about 1.5 inches thick.
 7. The filter of claim 1 wherein the fiber mat is bonded on one side to a mesh.
 8. The filter of claim 1 wherein the flexible locking connector is a cable tie.
 9. The filter of claim 1 wherein the inlet is a stormwater drain.
 10. The filter of claim 1 wherein the inlet is a roof drain.
 11. A method for reducing the amount of sediment which enters a drain, comprising placing a filter as described in claim 1 over the drain inlet and securing the filter to the grate by inserting the flexible locking connectors through the mat, passing each connector around a bar of the grate and back through the mat and locking each connector,
 12. A method for installing a filter on a drain inlet having a grate, comprising: providing a fiber mat of a size and shape to cover and slightly overlap the inlet; placing the mat over the inlet; and securing the mat to the drain.
 13. The method of claim 12 wherein securing the mat comprises attaching the mat to the grates by flexible locking connectors passed through the mat and around bars of the grate.
 14. The method of claim 13 wherein the flexible locking connectors are cable ties.
 15. The method of claim 12 wherein the fiber is selected from the group consisting of natural fiber, synthetic fiber, and blended natural and synthetic fiber.
 16. The method of claim 12 wherein the fiber mat has a density of about 4.0 OSF.
 17. The method of claim 12 wherein the fiber mat is about 1.5 inches thick.
 18. The method of claim 12 wherein the fiber mat is bonded on one side to a mesh.
 19. The method of claim 12 wherein the inlet is a stormwater drain.
 20. The method of claim 12 wherein the inlet is a roof drain and securing the mat comprises applying adhesive around the perimeter of the roof drain and the perimeter of one side of the mat to adhere the mat to the roof material around the perimeter of the roof drain. 